This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Recent genetic experiments have suggested an unprecedented speciation of iron within the mitochrondia of yeast, and in particular have provided evidence for two different pools of iron in mitochondria. This speciation effects the activity of mitochondrial superoxide dismutase (SOD), as iron from one pool is able to displace manganese from the active form of the enzyme, with the other iron pool is SOD-inert. XAS of WT and various mutant yeast mitochondria will be used to provide detailed local structural information for these two pools of mitochrondial iron.